On Sat, Feb 23, 2013 at 12:22 PM, Scott Klarenbach <sc...@pointyhat.ca> wrote:
> What is the best approach for creating a macro that parses sub-forms in any
> order, similar to the way (class ...) works in Racket?
I believe that there's support in the syntax-parse library to parse
these sub-forms in any order. Let me see if I can find the
appropriate documentation... Ah, here:
http://docs.racket-lang.org/syntax/Optional_Keyword_Arguments.html
The documentation here focuses on parsing optional keyword arguments
that can be consumed in any order. The underlying mechanism should
work with non-keywords as well.
For example:
;;;;;;;;;;;;;;;;;;;;;;;;;
#lang racket
(require (for-syntax syntax/parse))
(struct person (name age) #:transparent)
;; Accept name and age in any order, or even omit them:
(define-syntax (new-person stx)
(syntax-parse stx
[(_ (~or (~optional ((~datum name) name) #:defaults ([name #'"Jane Doe"]))
(~optional ((~datum age) age) #:defaults ([age #'#f])))
...)
#'(person name age)]))
(new-person)
(new-person (name "Pen Pen"))
(new-person (age 48) (name "Gendo Ikari"))
;;;;;;;;;;;;;;;;;;;;;;;;;
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